Frozen Vacherin Torte with Rhubarb Cream and Strawberries

Ingredients

• 0.3 teaspoon cream of tartar 
• 6 large egg whites 
• 5 large egg yolks 
• 2 tablespoons juice of lemon fresh
• 2 cups pieces rhubarb fresh (from 1 pound)
• 1 pinch salt 
• 0.8 cup strawberries hulled halved
• 0.5 cup sugar 
• 0.5 teaspoon vanilla extract 
• 0.3 cup water 
• 1 cup whipping cream chilled

Equipment

• bowl
• frying pan
• baking sheet
• sauce pan
• baking paper
• oven
• whisk
• hand mixer
• cake form
• kitchen thermometer
• aluminum foil
• springform pan
• pastry bag

Directions

1. Position racks in top third and center of oven and preheat to 250°F. Using 8-inch-diameter bowl or plate as guide, firmly trace 2 circles onto 1 sheet of parchment paper and 1 circle onto second sheet of parchment.
2. Place papers, marked side down, on 2 baking sheets. Spray paper with nonstick spray.
3. Using electric mixer, beat egg whites in large bowl until frothy.
4. Add cream of tartar and salt; beat until soft peaks form. Beat in sugar, 1 tablespoon at a time, then beat until whites are stiff and glossy. Beat in vanilla. Working in batches, spoon meringue into large pastry bag fitted with 1/2-inch plain tip. Starting in center of each traced circle and holding tip just above paper, pipe meringue in spirals to fill circles, forming 3 rounds.
5. Bake meringues until firm, dry, and pale golden, about 2 hours. Turn off oven; leave meringues in oven with door closed at least 4 hours or overnight.
6. Combine rhubarb, strawberries, 1/2 cup sugar, water, and lemon juice in saucepan. Bring to boil, stirring to dissolve sugar. Reduce heat and simmer until rhubarb is very tender, about 15 minutes. Puree mixture in processor. Chill until cold, about 1 hour.
7. Whisk yolks and 1/3 cup sugar in large metal bowl to blend. Set bowl over saucepan of simmering water (do not allow bowl to touch water).
8. Whisk until mixture thickens and instant-read thermometer registers 140°F for 3 minutes, about 7 minutes total. Chill mixture until cool, about 15 minutes. Gently fold rhubarb mixture into yolk mixture. Using electric mixer, beat whipping cream and vanilla in another large bowl until stiff peaks form. Fold cream into rhubarb mixture in 2 additions.
9. Place 1 meringue disk in 9-inch-diameter springform pan.
10. Spread 1/3 of rhubarb cream (about 1 1/2 cups) over meringue, leaving 1/2-inch plain border. Top with second meringue disk, then 1/3 of rhubarb cream. Top with remaining meringue disk and rhubarb cream (cream will not spread to sides of pan). Freeze until cream is firm, about 6 hours. (Can be made 4 days ahead. Cover with foil; keep frozen.)
11. Release cake pan sides.
12. Serve torte with sweetened strawberries, if desired.